Behavioral and/or biochemical teratogenesis, as an entity, has been suggested by a host of studies in animals with drugs or chemicals. The most compelling argument supporting the possibility that chemicals may induce functional teratogenesis in man comes from the methylmercury tragedies during the last 25 years. However, many of the animal studies have employed doses of substances that produced embryotoxicity or frank teratogenesis, questioning the validity of these methods for demonstrating functional teratogenesis. Because l-alpha-acetylmethadol appears to be gaining acceptance as a probable substitute for methadone, we propose a longitudinal study of the effects of exposure to LAAM during various stages of development. The drug (or its metabolites) will be administered to pregnant rats or injected into fertilized chicken eggs to determine if: 1. Behavioral and/or biochemical teratogenesis can be induced by LAAM at realistic doses calculated and estimated to be sufficient to maintain a morphine-dependent rat and do not induce embryotoxicity. 2. Critical periods exist for these phenomena. 3. Withdrawal from LAAM has consequences upon postnatal behavior or CNS function.